Chapter 9.6

When sketching the graph of a new type of equation, it is often helpfulto locate the intercepts.

To find an equation for a circle given the center = (3,12) and radius = 5
(x-3)^2 + (y-12)^2 = 5^2

to find any point on a circle thats not on the x or y axis use the equation:
x^2+y^=r^2




Center (0,0), radius 9
x square 2 + y square 2 = 81

Center (1,3), radius 4
(x+1) square 2 + (y +3) square 2 = 16

Examples:
Find the center and ratio of each circle:
25. x^2+y^2=100 answer: (0,0) R=10
27.x^2 + y^2=101 answer:(0,0) R=the square root of 101
29. x^2 + (y-3)^2=4 answer: (0,3) R=2
31.y^2+(x+3)^2=49 answer:(-3,0) R=7